Hexaarylbiimidazole-coumarin compositions



0d. 1 3., 1970 5, JAMES ETAL 3,533,797

HEXAARYLBIIMIDAZOLECOUMARIN COMPOSITIONS Filed March 13, 1967 INVENTORS DANIEL s. JAMES" VINCENT G. WITTERHOLT w ATTORNEY 3,533,797 HEXAARYLBIIMIDAZOLE-COUMARIN COMPOSITIONS Daniel S. James, Hockessin, and Vincent G. Witterholt, Wilmington, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed Mar. 13, 1967, Ser. No. 622,526 Int. Cl. G03c 1/72 U.S. Cl. 96-90 15 Claims ABSTRACT OF THE DISCLOSURE Photoactivatible compositions comprising, basically, a hexaarylbiimidazole and a se ected substituted coumarin having absorption maximally in the near ultraviolet region. The basic composition can be combined with a leuco dye alone or with a lecuo dye and a fixing system. The compositions may be employed with inert solvents, plasticizers and/ or binders. A cathode ray tube print-out system is also described.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to photoactivatible compositions. More specifically, the invention concerns various near ultraviolet sensitive compositions containing a photodissociable hexaaryl'biimidazole that absorbs radiation maximally in the ultraviolet at realtively short wavelengths, and a coumarin sensitizer (i.e., an energy-transfer agent) that absorbs radiation substantially in the ultraviolet at relatively long wavelengths.

Description of the prior art Compositions of hexaarylbiimidazoles and leuco dyes are knownto be photosensitive. They form colored images upon exposure to ultraviolet radiation. These images can be permanently fixed if a fixing system is added to the original composition. The biimidazole component, upon irradiation, photolyzes and dissociates to the colored triarylimidazolyl radical. This radical then oxidizes the leuco to its dye form, whereupon the dye form becomes fixed due to deactivation of the biimidazole by reaction with the fixing system. Thus, the entire sequence is dependent upon the photolization of the biimidazole. However, the hexaarylbiimidazoles in general absorb largely and maximally at ultraviolet (UV) wavelengths below 300 mp Thus, while any of the imaging compositions described above containing the biimidazole are sensitive to radiation over substantially the whole UV range, they respond most efiiciently to radiation that corresponds to or substantially overlaps the region of maximum absorption; and it is not always practical to irradiate fu ly into this region. For example, in some imaging applications, it is desired to cover the photosensitive biimidazole-leuco dye imaging composition with a transparent film. Some film materials, such as Mylar and Cronar commercial polyesters, otherwise suitable, are not transparent below 300 m and thus prevent such short wavelength activating radiation from reaching the biimidazole, with consequent loss in efficiency.

Further, many commercially important ultraviolet sources, such as cathode ray tubes widely useful in imaging devices that convert electrical to light energy and transmit such light as images to photosensitive surfaces (plates, papers, films), emit mainly in the near ultraviolet and above, owing in part to limitations in the available phosphors and in part to the screening by the fiber optic face plate of radiation below 300 mn. Thus, imaging with United States Patent ice.

such radiation sources is not entirely satisfactory as to the imaging speeds and optical densities that the hiimidazole/ leuco dye systems can inherently provide.

Thus, as the activating radiation contain increasing proportions of visible components or as components closer to the UV region are filtered out, hexaarylbiimidazole photolysis, hence color formation from leuco dye, becomes less etficient as to the amount of energy utilized and the optical quality of the image produced.

The present invention overcomes these deficiencis by enhancing the efficiency of the imaging systems described abov in the near ultraviolet region of absorption through the use of selected coumarins.

SUMARY OF THE INVENTION This invention is based on the surprising discovery that substituted coumarins as defined below, which strongly absorb ultraviolet light at longer wavelengths than the biimidazoles, can transfer such absorbed longer wavelength light energy to the biimidazoles. By thus enhancing the spectral sensitivity of the biimidazoles at Wavelengths they normally poorly absorb, the coumarins significantly enhance their utility as light screens and photooxidants.

While the sensitization mechanism is not known with certainty, it is considered that when compositions of this invention comprising a relatively short wevelength absorbing biimidazole and a relatively longer wavelength absorbing coumarin sensitizer as defined are irradiated with such relatively longer Wavelength light inthe range 300-400 my, the biimidazole is only weakly affected, i.e., a substantial proportion of the biimidazole molecules remain in the ground (unactivated) state. The sensitizer, however, responding directly, absorbs the light more fully and is actiavted to at least one excited energy transfer state. In such state, the activated coumarin transfers absorbed energy to the biimidazole, for example through collision or resonance interaction, and returns to the ground state, thus becoming available again for activation. The thusindirectly-activated biimidazole molecules dissociate into imidazolyl radicals.

The overall sensitization process can be represented as (1a) radiation 300 mu weak or no activation (1b) radiation 300-400 mu 3 (2) S* LL S+LL* LL* 2L.

where C is the coumarin sensitizer; 8* its activated energy transfer state; LL is the biimidazole (dimer), LL* its activated, dissociable state; and L. is the resulting imidazolyl radiacl.

The subsequent fate of the inherently co ored and energy-rich imidazolyl radicals and their utilization in accordance with the various embodiments of this invention depends on the substantial absence or presence of other substances that are reactive towards the radicals. Thus, in formulating light screens or windows containing biimidazole/sensitizer compositions of this invention, there will usually be employed other components, such as solvents, plasticizers, and binders that are substantially inert, i.e., resistant, to oxidation by the imidazolyl radicals. In such an embodiment, the sensitization process manifests itself as a color change, attributable to formation of the inherently color triarylimidazolyl radical (Equation 3). When the light source is removed, the color fades as the radicals dimerize (Equation 4) to the biimidazole:

The imidazolyl radicals are useful oxidants, as schematically illustrated in Equation where DH for example is an oxidizable substance such as a leuco dye, D is the oxidation product (dye), and LH is the reduction product (a triarylimidazole in this instance).

Thus, the biimidazole/sensitizer combinations are particularly useful as photo-actuated photooxidants for a variety of substrates, including leuco dyes, and the biimidazole/sensitizer/leuco dye combinations constitute the basic ingredients of widely useful photo-actuated imaging systems, as more fully described be ow.

The basic composition then of this invention comprises:

(a) a hexaarylbiimidazole that absorbs in the ultraviolet principally at wavelengths below 300 me and is dissociable to triarylimidazolyl radicals by such radiation, and

(b) a coumarin which has a light absorption maximum in the ultraviolet at wavelengths greater than 300 m that is stronger than the absorption of the biimidazole at such wavelengths, and is capable of transferring the absorbed energy corresponding to such wavelengths to the biimidazole.

Other embodiments of the invention comprise the above basic composition in combination with other components of an imaging system. For example, another composition of the invention comprises a composition of (a) and (b) defined above, and (c) a leuco dye.

Still another composition of the invention comprises (a), (b) and (c) defined above, and (d) a fixing component, e.g., a redox couple defined further below.

It is understood that any of the above compositions of this invention can also contain solvents, plasticizers, polymeric binders, and/or carriers which do not alfect the ultraviolet absorption or the imaging properties of the primary ingredients.

DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION OF THE INVENTION (A) The coumarin component The coumarins operable in the compositions of this invention are those of the formula wherein X and Y are each hydrogen, lower alkyl or lower alkoxy;

Z is hydrogen, lower alkyl, lower alkoxy or dilower alkylamino;

W is hydrogen, lower alkyl, phenyl containing a lower alkoxy group in the 0- or p-position, and phenyl containing a substituted amino group in the 0- or p-position; and wherein at least one of W and Z is other than hydrogen or lower alkyl. Stated differently, the coumarin must contain at least one of the dialkylamino, alkoxy, alkoxyphenyl or aminophenyl groups in the 3- or 7-position.

These coumarins absorb maximally in the 300-400 mg region, particularly in the 340-390 mg region.

The 7-diloweralkylamino-4-lower alkyl coumarins are a preferred subclass which include 7-dimethylamino-4- butyl coumarin, 7-diethylamino-4-ethyl coumarin, 7-dibutylamino-4-methyl coumarin, and the more preferred sensitizers 7-dl'rnethylamino-4-methyl coumarin [avail- 4 able as Calcofiuor White LD (A max. 360 my in EtOH, e=20,700)] and 7 diethylamino 4 methyl coumarin [available as Calcofluor White RW (A max. 375 m in EtOH, e=22,000)].

Another subclass encompasses the 7-lower alkoxycoumarins such as 7-methoxycoumarin, 7-ethoxycoumarin, 7- propoxycoumarin, 7-butoxycoumarin, 5,7-dimethoxycoumarin. Still another subclass includes the 3-(orthoor para-alkoxyphenyl)coumarins such as 3-(p-methoxyphenyl)coumarin, 3-(o-methoxyphenyl)coumarin, 3-(pethoxyphenyl) 7 methylcoumarin, 3-(p-butoxyphenyl) coumarin, 3-(p-methoxy-S-methylcoumarin), and 3 (o-,pdimethoxyphenylcoumarin. ,Still another substituted coumarin sensitizer is commercially available as Tinopal PG, which has the formula The quantity of coumarin sensitizer employed may vary widely. It will normally amount to .1 to 2 moles/mole of the biimidazole, and preferably about .4 to .6 moles per mole of biimidazole.

In contrast, other coumarins, such as coumarin, 3- carbethoxycoumarin, 6 chlorocoumarin, 7 hydroxy-4- methylcoumarin, and 6,7-dihydroxy-4-methyl-coumarin, known as optical brighteners for other photochemical systems, are much less or not all efiective to sensitize biimidazole photolysis and the imaging reaction.

It has also been found that 3,3-diethylthiacyanine iodide (A max. 428 mu), itself a poor sensitizer for the biimidazole-leuco dye imaging system, is highly and synergistically effective in combination with a near-UV absorbing coumarin-type sensitizer, such as 7-diethylamino-4-methyl coumarin (A max. 375 m affording increased imaging speeds and higher optical densities, particularly when irradiated with phosphor emissions extending from the near UV into the visible, and peaking at 450 my.

(B) The hexaarylbiimidazole component wherein A, B and D represent aryl groups which can be the same or different, carbocyclic or heterocyclic, unsubstituted or substituted with substituents that do not interfere with the dissociation of the biimidazole to the imidazolyl radical or with the oxidation of the leuco dye, and each dotted circle stands for four delocalized electrons (i.e., two conjugated double bonds) which satisfy the valences of the carbon and nitrogen atoms of the imidazolyl ring.

The aryl groups include oneand two-ring aryls, such as phenyl, biphenyl, naphthyl, furyl and thienyl. Suitable inert substituents on the aryl groups have Hammet sigma (para) values in the .5 to 0.8 and are free of Zerewitnoff hydrogen, i.e., have no hydrogens reactive towards methyl magnesium iodide. Representative substituents and their sigma values (relative to H=.00), as given by Jalfe, Chem. Rev. 53, 219-233 (1953) are: methyl (0.17), ethyl (0.15), t-butyl (0.20), phenyl (0.22), trifluoromethyl (0.55), chloromethyl (0.18), cyanomethyl (0.01), 2-carboxyethyl (-0.07), butoxy (0.32), phenoxy (-0.03), fiuoro (0.34), chloro (0.37), bromo (0.39), iodo (0.35), methylthio (0.05), methylsulfonyl (0.73), nitro (0.78), methoxycarbonyl (0.64), and cyano (0.63). Thus, the substituents may be halogen, cyano, lower hydrocarbyl (including alkyl, halo alkyl, cyanoalkyl, and aryl), alkoxyl, aryloxy, alkylthio, arylthio, alkyl sulfonyl, arylsulfonyl, and nitro. In the foregoing list, alkyl groups referred to therein are preferably of 16 carbon atoms; while aryl groups referred to therein are preferably of 6-10 carbon atoms.

Preferably the aryl radicals are carbocyclic, particu larly phenyl, and the substituents have Hammet sigma values in the range .4 to +.4, particularly lower alkyl, lower alkoxy, Cl, F and Br groups.

In a preferred biimidazole class, the 2 and 2 aryl groups are phenyl rings bearing an ortho substituent having a Hammett sigma value in the range .4 to +4. Preferred such ortho substituents are fluorine, chlorine, bromine, lower alkyl and alkoxy groups; especially chloro.

Most preferably, the 2-phenyl ring carries only the above-described ortho group, and the 4- and 5-phenyl rings are either unsubstituted or substituted with lower alkoxy.

Representative hexaarylbiimidazoles which may be used in the practice of this invention are:

2,2-bis o-bromophenyl -4,4,5 ,5 '-tetraphenylbiimidazole,

2,2'-bis (p-bromophenyl) -4,4',4,4-tetraphenylbiimidazole,

2,2.-bis (p-carboxyphenyl) -4,4,5 ,5 'tetraphenylbiimidazole,

2,2'-bis (o-chlorophenyl -4,4',5 ,5 -tetrakis p-methoxyphenyl )biimidazole,

2,2-bis (o-chlorophenyl) -4,4, 5 ,5 '-tetraphenylbiimidazole,

2,2'-bis (p-chlorophenyl) -4,4,5 ,5 -tetrakis (p-methoxyphenyl) biimidazole,

2,2-bis p-cyanophenyl) -4,4',5 ,5 '-tetrakis (p-methoxyphenylbiimidazole,

2,2'-bis 2,4-dichlorophenyl -4,4',5 ,5 -tetraphenylbiimidazole,

2,2'-bis (2,4-dimethoxyphenyl) -4,4,5 ,5 '-tetraphenylbiimidazole,

2,2'-bis (o-ethoxyphenyl) -4,4,-5 ,5 '-tetr aphenylbiimidazole,

2,2-bis (m-fiuorophenyl) -4,4,5 ,5 -tetraphenylbiimidazole,

2,2'-bis (o-fiuorophenyl -4,4,5 ,5 '-tetraphenylbiimidazole,

2,2'-bis (p-fluorophenyl) -4,4',5 ,5 -tetraphenylbiimidazole,

2,2'-bis (o-hexoxyphenyl) -4,4,5 ,5 '-tetrapheny1biimidazole,

2,2-bis o-hexylphenyl) -4,4',5 ,5 '-tetrakis p-methoxyphenyl biimidazole,

2,2'-bis 3,4-methylenedioxyphenyl) -4,4,5 ,5 -tetraphenylbiimidazole,

2,2-bis orchlorophenyl) -4,4',5 ,5 -tetrakis (m-methoxyphenyl) biimidazole,

2,2-bis (o-chlorophenyl )-4,4',5 ,5 -tetrakis [m- (betaphenoxyethoxyphenyl) biimidazole,

2,2-bis (2,6-dichlorophenyl) -4,4,5 ,5 '-tetraphenylbiimidazole,

2,2"-bis (o-methoxyphenyl) -4,4,5 ,5 '-tetraphenylbiimadazole,

2,2'-bis (p-methoxyphenyl) -4,4-bis (o-methoxyphenyl 5,5 '-diphenylbiimidazole,

2 ,2-bis o-nitrophenyl) -4,4,5 ,5 -tetraphenylbiimidazole,

2,2'-bis (p-phenylsulfonylphenyl) -4,4,5 ,5 -tetraphenylbiimid azole,

2,2'-bis (p-sulfamoylphenyl) -4,4',5 ,5 -tetraphenylbiimid azole,

2,2-bis (2,4,6-trimethylphenyl) -4,4' ,5 ,5 '-tetraphenylbiimidazole,

2,2-di-4-biphenyl-4,4',5 ,5 '-tetraphenylbiimid azole,

2,2'-di-l-naphthyl-4,4,5 ,5 -tetrakis (p-methoxyphenyl biimid azole,

6 2,2-di-9-phenanthryl-4,4',5 ,5 '-tetrakis (p-methoxyphenyl)biimidazole, 2,2'-diphenyl-4,4',5 ,5 '-tetra-4-biphenylylbiirnidazole, 2,2-diphenyl-4,4',5 ,5 -tetra-2,4-Xylylbiimidazo1e, 2,2'-di-3-pyridyl-4,45 ,5 '-tetraphenylbiimidazole, 2,2'-di-3-thienyl-4,4,5 ,5 -tetraphenylbiimidazole, 2,2-di-o-tolyl-4,4,-5 ,5 '-tetraphenylbiimidazole, 2,2-di-p-tolyl-4,4',5 ,-5 '-di-o-tolyl-5 ,5 '-diphenylbiimidazole, 2,2'-di-2,4-xylyl-4,4',5 ,5 -tetraphenylbiimidazole, 2,2',4,4,5 ,5 -hexakis(p-benzylthiophenyl)biimidazole, 2,2,4,4,5 ,5 '-hexa-l-naphthylbiimidazole, 2,2',4,4,5 ,5 -hexaphenylbiirnidazole, 2,2-bis( 2-nitro-5 -methoxyphenyl) -4,4',5 ,5 '-tetraphenylbiimidazole, and 2,2-bis (o-nitrophenyl -4,4',5 ,5 '-tetrakis (m-methoxyphenylbiimidazole.

The biimidazoles are conveniently obtained by known methods as more particularly described b Italian Patent 707,086 and by Hayashi et al., Bull. Chem. Soc. Japan, 33, 565 (1960). The preferred method, involving oxidative dimerization of the corresponding triarylimidazole with ferricyanide in alkali, generally yields the l,2'-biimidazoles, although other isomers, such as the 1,l,l,4', 2,2',2,4' and 4,4'-biimidazoles are sometimes also obtained admixed with the l,2-isomer. For the purposes of this invention, it is immaterial which isomer is employed so long as it is photodissociable to the imidazolyl radical as discussed above.

Biimidazoles useful in this invention are descrbed in South African patent application 3627/63, published August 12, 196, and in British Pat. 997,396, published July 7, 1965.

(C) The leuco dye component The leuco dye component together with the basic composition forms one embodiment of this invention. By the term leuco dye is meant the colorless (i.e., the reduced) form of a dye compound which upon oxidation becomes colored. When present in the composition of this invention, it is oxidized to its colored form by the imidazolyl radical.

Leuco dyes which may be oxidized to color by triarylimidazolyl radicals generated by this invention include: aminotriarylmethanes, aminoxanthenes, aminothioxanthenes, amino-9,IO-dihydroacridines, aminophenoxazines, aminophenothiazines, aminodihydrophenazines, aminodiphenylmethanes, leuco indamines, aminohydrocinnamic acids (cyanoethanes, leuco methines), hydrazines, leuco indigoid dyes, amino-2,3-dihydroanthraquinones, tetrahalo-p,p' biphenols, 2(p-hydroxyphenyl)-4,5-diphenylimidazoles, phenethylanilines, IO-acyI-aminodihydrophenazines, lO-acyl-aminophenothiazines, IO-acyI-aminophenoxazines; aminotriarylmethanes wherein the methane hy drogen has been replaced by alkylthio, benzylthio, 2- phenylhydrazino, or alkoxycarbonyl; aminotriarylmethanes wherein two aryl groups are substituted with a disubstituted amino and an alkyl group and the third aryl is p-alkylthio-, p-arylthio-, aralkylthiophenyl, Z-thienyl, 2-furyl,3,4-methylenedioxyphenyl, 2-methoxy-4- (C to C )alkoxyphenyl or 3,4-di(C to C )a1koxyphenyl.

Leuco triarylmethane dyes that contain tertiary amino groups are preferred, particularly those wherein (1) at least two aryls are phenyls having (a) a para-R R substituent, Where R and R are C -C alkyl, Z-hydroxyethyl, 2-cyanoethyl, benzyl or phenyl, and (b) an ortho C -C alkyl, C -C alkoxy, fluoro, chloro, or bromo-substituent, and (2) the third aryl, when different from the first two, is thienyl, furyl, phenyl or phenyl substituted with one or more C -C alkyl, C -C alkoxyl, methylenedioxy, fluoro, chloro, bromo, amino, alkylamino, dialkylamino, alkylthio, hydroxy, carboxy, carbonamido, carbalkoxy, lower alkylsulfonyl, lower alkylsufonamido, arylsulfonamido, nitro, or benzylthio groups. Representa- 7 tive aminotriarylmethanes that may be used in this invention follow:

his 2-bromo-4-diethy1aminophenyl phenylmethane,

bis 2-butoxy-4-diethylaminophenyl phenylmethane,

bis[4 (2-cyan0ethyl)(2 hydroxyethyl)amino-o-tolyl]- (p-benzylthiophenyhmethane,

bis[4 (2-cyanoethyl)(2 hydroxyethyl)amino-otolyl} Z-thienylmethane,

bis(4-dibuty1amino-o-toly1) Z-thienylmethane,

bis(4-diethy1amnio-2-ethylphenyl) (3,4 methylenedioxyphenyl)-methane,

bis(4-diethylamino-2 fluorophenyl) (p-benzylthiophenyl) methane,

bis(4-diethylamino-2 fluorophenyl) (3,4-methylenedioxyphenyl)methane,

bis(4 diethylamino-2 methoxyphenyl) (p-nitrophenyl) methane,

bis(4 diethylamino-l-naphthyl)(4-diethylamnio-o-tolyl) methane,

bis(4 diethylamino-o-tolyl) (p-benzylthiophenyl)methane,

bis(4 diethylamino-o-tolyl) (2,4-dimethoxyphenyl)methane,

bis(4-diethylamino-o-tolyl)Z-furylmethane,

bis(4 diethylamino-o-tolyl) (p-methoxyphenyl)methane,

bis(4 diethy1amino-o-to1yl)3,4 methylenedioxyphenyl) methane,

bis(4 diethylamino-o-tolyl)(p-methylthiophenyl)methane,

bis(4-diethylamino-o-tolyl) l-naphthylmethane,

bis(4-diethylamino-o-tolyl)phenylmethane,

bis(4-diethylamino-o-toly1)Z-thienylmethane,

tris(4-dimethylamino-2-chlorophenyl)methane,

bis(4 dimethylamino-2,5-dimethy1phenyl)phenylmethane,

bis( 4 dimethylamino2-hexylphenyl) (p-butylthiophenyl) methane,

bis(4 dimethylamino-o-tolyl) (o-bromophenyl)methane,

bis[4 (N-ethylanilino)-o-tly1](3,4 dibutoxyphenyl) methane,

bis(4 ethylbenzylamino o-tolyl)(p-methoxyphenyl) methane,

bis [4-bis(2-hydroxyethyl) amino-Z-fluorophenyl] (pbenzylthiophenyl)methane,

tris(4-diethylarnino-o-tolyl)methane, and

tris(p-dioctylamino-o-tolyl)methane.

bis (4-diethylamino-o-tolyl -p-ch1orophenyl methane bis (4-diethylamino-o-toly1) -p-bromophenyl methane bis 4-diethylamino-o-tolyl -p-fluoropheny1 methane bis(4-diethylamino-o-to1yl)-p-toly1 methane bis(4 diethylamino-o-tolyl)-4-methoXy-1-naphthyl methane bis(4 diethylamino-o-tolyl) 3,4,5 trimethoxyphenyl methane bis 4-diethylamino-otolyl -p-hydroxyphenyl methane bis(4 diethylamino-o-tolyl) 3-methy1thienyl methane 5 [bis 4-diethy1amino-o-tolyl -methyl] -2,3 -cresotic acid 4- [bis (4-diethylamino-o-tolyl) -methy1] -phenol 4- [bis (4-diethylamino-o-toly1 -methyl] -acetanilide 4- [bis (4-diethylamino-o-tolyl -methyl] -phenylacetate 4- [bis (4-diethylamino-o-tolyl -methy1] -benzoic acid 4-[bis(4-diethylamino-o-tolyl) -methy1] -diphenyl sulf one 4-['bis(4 diethylamino-o-tolyl)-methy1] phenylmethyl sulfone 4-[bis(4 diethylamino-o-tolyl)-methyl] methylsulfonanilide 4-[bis(4 diethylamino-o-tolyl)-methyl] p-tolylsulfonanilide bis(4 diethylamino-o-tolyl)-p-nitrophenyl methane These amino substituted cationic dye precursors are generally employed in the color forming process as salts of strong acids, including Lewis acids, such as hydrochloric, hydrobromic, sulfuric, nitric, phosphoric, acetic,

oxalic, p-toluenesulfonic, zinc chloride, zinc bromide, and

ferric chloride, the proportion of acid varying from 0.33 mole to 1 mole per amino group.

Representative leuco compounds of the other classes are as follows:

Aminoxanthenes 3-amino-6-dimethylamino-2-methyl-9-(o-chlorophenyl) anthene 3 -arnino-6-dimethylamino-2-methyl-9-phenylxanthene 3 -amino- 6-dimethylamino-2-methylxanthene 3 ,6-bis(diethylamino)-9-(o-chlorophenyl)xanthene 3 ,6-bis(diethylamino)-9-hexylxanthene 3 ,6-bis(diethylamino)-9-(o-methoxycarbonylphenyl) xanthene 3 ,6-bis(diethylamino)-9-methylxanthene 3 ,6-bis(diethylamino)-9-phenylxanthene 3 ,6-bis(diethylamino)-9-o-tolylxanthene 3 ,6-bis(dimethylamino)-9-(o-chlorophenyDxanthene 3,6-bis(dimethylamino)-9-ethy1xanthene 3 ,6-bis(dimethylarnino)-9-(o-methoxycarbonylphenyl) Xanthene 3,6-bis(dimethylarnino)-9-methylxanthene.

Aminothioxanthenes 3, 6-bis(diethylamino)-9-(o-ethoxycarbonylphenyl) thioxanthene 3,6-bis(dimethylamino)-9-(o-methoxycarbonylphenyl) thioxanthene 3 ,6-bis(dimethylamino)thioxanthene 3,6-dianilino-9-(o-ethoxycarbonylphenyDthioXanthene Amino-9,lO-dihydroacridines 3,6-bis(benZylamino)-9,10-dihydro-9-methylacridine 3,6-bis(diethylamino)-9-heXyl-9,IO-dihydroacridine 3,6-bis(diethylamino)-9,10-dihydro-9-methy1acridine 3,6-bis(diethylamino)-9,10-dihydro-9-phenylacridine 3,6-diamin0-9-heXyl-9, 1 O-dihydroacridine 3,6-diamino-9,10-dihydro-9-methylacridine 3,6-diamino-9,10-dihydro-9-phenylacridine 3,6-bis(dimethylamino)-9-heXyl-9, IO-dihydroacridine 3,6-bis(dimethy1amino)-9,10-dihydro-9-methylacridine.

Aminophenoxazines 3,7-bis(dimethylamino)phenoxazine 3,7-bis(diethylamino)phenoxazine 3,7-bis(dibutylamino)phenoxazine 3-diethylamino-7-dimethylamino-2-methylphenoxazine 3-dimethylamino-7-dipropylaminophenoxazine 5 -dimethylamino-9-diethylamino-1ZH-benzo[a] phenoxazine 5-dibenzylamino-9-diethylamino-12H-benzo[a] phenoxazine 5 ,9-bis(diethylamino)-12H-benzo[a] phenoxazine Acylation gives the corresponding 10-acy1 compounds.

Aminophenothiazines 9 3,7-diamino-5,10-dihydro-S-methylphenazine 3,7-diamino--hexyl-5,IO-dihydrophenazine 3,7-bis(dimethylamino)-5,10-dihydrophenazine 3,7-bis(dimethylamino)-5,10-dihydro-5-phenylphenazine 3,7-bis (dimethylamino)-5 -dihydro-5-methy1phenazine Acylation gives the corresponding IO-acyl compounds.

Aminodiphenylmethanes 1,4-bis [bis-p(diethylaminophenyl)methyl] piperazine bis(p-diethylaminophenyl)anilinomethane bis(p-diethylarninophenyl)-l-benzotriazolylmethane bis(p-diethylaminophenyl)-2-benzotriaz0lylmethane bis(p-diethylaminophenyl)(p-chloroanilino)methane bis(p-diethylaminophenyl)(2,4-dichlqroanilino)methane bis(p-diethylaminophenyl)(methylamino)methane bis(p-diethylaminophenyl)(octadecylamino)methane bis(p-dimethylaminophenyDaminomethane bis(p-dimethylaminophenyl)anilinomethane 1,1-bis(dimethylaminophenyl)ethane 1,1-bis(dimethylaminophenyl)heptane bis(4-methylamino-m-tolyl)aminoethane.

Leuco indamines 4-amino-4-dimethylaminodiphenylamine p-(p-dimethylaminoanilino)phenol Aminohydrocinnarnic acid (cyanoethanes, leuco methines) Hydrazines 1- (p-diethylaminophenyl) -2- (2-pyridyl) hydrazine 1- (p-dimethylaminophenyl -2- (2-pyridyl) hydrazine 1-( 3 -methyl-2-b enzothiazolyl) -2- (4-hydroxy-1-naphthyl hydrazine 1- (Z-naphthyl) -2-phenylhydrazine 1-p-nitrophenyl-2-phenylhydrazine 1-( 1,3 ,3 -trirnethyl-2-indolinyl) -2- 3-N-phenylcarb amoyl-4-hydroxyl-naphthyl) hydrazine Lenco indigoid dyes The leuco forms of indigoid dyes having CI numbers 73000, 73015, 73025, 73030, 73035, 73040, 73045, 73050, 73055, 73060, 73065, 73070, 73085, 73090, 73110, 73300, 73305, 73310, 73315, 73320, 73325, 73335, 73340, 73345, 73350, 73360.

Amino-2,3-dihydroanthraquinones 1,4-dianilino-2,3-dihydroanthraquinone 1,4-bis ethylamino) 2,3-dihydro anthraquinone Phenethylanilines N- (Z-cyano ethyl) -p-phenethylaniline N,N-diethyl-p-phenylethylaniline N,N-dimethyl-p- [2-( l-naphthyl ethyl] aniline N,N-dimethyl-p- [2- (4-nitr0-1 -naphthyl ethyl] aniline N,N-dimethyl-p-phenethylaniline N,N-dimethyl-p- [2- (4-meth0Xy-l-naphthy1 ethyl] aniline p- (p-methoxyphenethyl) aniline p- [2-( l-naphthyl) ethyl] aniline p-(p-nitrophenethyl aniline p-phenethylaniline Alkyland benzylthio derivatives of aminotriarylmethane tris (p-dimethylaminophenyl) benzylthiomethane bis (p-dimethylaminophenyl) -p-dipropylaminophenylbenzylthiomethane bis (p-dimethylaminophenyl) -p-propoxyphenylbenzylthiomethane bis (p-diethylaminophenyl) -p-cyanophenylb enzylthiomethane bis p-diethylaminophenyl) -p-chl0rophenylbenzy1 thiometh ane bis (p-diethylaminophenyl) -p-flu0rophenylb enzylthiomethane bis (p-diethylaminophenyl -p-pentoxyphenylbenzylthiomethane bis (p-diethylaminophenyl) -p-carbamoylphenylbenzylthiomethane bis (p-diethylaminophenyl) -pnitrophenylbenzylthiomethane bis (4-diethy1aminobmethoxyphenyl -p-ethylphenylmethylthiomethane bis (4-diethylamino-2-propoxyphenyl -2-chloro-4- octylphenylethylthiometh ane bis (p-diethylaminophenyl -2,4-dimethoxyphenylpro pylthiomethane bis pdiethylaminophenyl) -4-bromo-2-methoxypheny1- butylthiomethane Z-Phenylhydrazino derivatives of aminotriarylmethane 1 -tris p-diethylaminophenyl methyl-Z-phenylhyd razine l-tris 4-diethylamino-2-chlorophenyl) methyl-2- phenylhydrazine l-tris 4-diethylamino-o-tolyl) methyl-Z-phenylhydrazine 1- [bis (p-di-methylaminophenyl) phenylmethyl] -2- phenylhydrazine 1- [bis (4-dimethylamino-2-methoxyphenyl -p-nitr0- phenylmethyl] -2-phenylhydrazine 1- [bis (p-dip ropylaminophenyl) -2,4-dichlorophenylmethyl] -2-phenylhydrazine Alkoxycarbonyl derivatives of aminotriarylmethane tris (p-dimethylaminophenyl )ethoxycarbonylmethane (or ethyl tris (p-dimethylaminophenyl) acetate) tris (p-dibutylarninophenyl) pentoxyc arbonylmethane tris(4-didodecylamino-o-tolyl methoxycarbonylmethane tris [4- (N-ethyl-N-phenylamino) -2-ethylphenyl] ethoxycarbonylmethane tris [4-bis(2-methoxyethyl) amino-2-bromophenyl] ethoxycarbonylmethane tris [4-bis Z-cyanoethyl) amino-2-chlorophenyl] ethoxycarbonylmeth ane tris [4-bis (Z-hydroxyethyl) amino-Z-fluorophenyl] ethoxycarb onylmethane tris (4-dibenzylamino-2-pentoxypheny1) ethoxycarbonylmethane Aminotriarylrnethanes having specified aryl groups Bis [4- N-benzyl-N-ethylarnino -o-tolyl] (p-benzylthiophenyl) methane Bis [4-bis (2-cyanoethyl) amino-o-tolyl] (p-benzylthiophenyl methane Bis [4bis Z-ethoxyethyl amino-otolyl] (p-benzylthiophenyl) cyanomethane Bis [4-bis Z-hydroxyethyl) amino-Z-ethylphenyl] (pbenzylthiophenyl methane Bis [4-bis 2-hydroxyethyl) amino-Z-fiuorophenyl] (pbenzylthiophenyl methane Bis[4-bis(2-hydroxyethyl) amino-Z-fiuorophenyl] (pbenzylthiophenyl methane Bis 4-bis 2-hydroxyethyl amino-Z-fluorophen yl] (pbenzylthio-m-butylphenyl) methane Bis (4-diethylamino-o-tolyl) (p-benzylthiophenyl) cyanomethane Bis 4-diethylamino-o-tolyl) (p-phenylthiophenyl methane Bis 4-diethylamino-o-tolyl) [p- (o-tolylthio phenyl] methane Bis [4-bis 2-cyanoethyl)amino-o-tolyl] (3,4-dibutoxyphenyl methane Bis [4-bis Z-cyanoethyl) amino-o-tolyl] Z-furylmethane Bis [4-bis 2-cyan0 ethyl aminoo--tolyl] (3 ,4-dibutoxyoxyphenyl cyanomethane Bis 4-bis 3-hydroxypropyl) amino-o-tolyl] (Z-methoxy- 4-octyloxyphenyl) methane Bis [4-bis 2-methoxyethyl amino-o-tolyl] (3,4-methylenedioxyphenyl) methane Bis 4-dibenzylarnino-o-tolyl) Z-thienylmethane Bis (4-dimethylamino-Z-ethylphenyl) (3 ,4-methylenedioxyphenyl methane Bis 4-dimethylamino-Z-ethylphenyl) Z-thienylcyanomethane Bis (4-dimethylamino-o-tolyl) (2,4-dimethoxyphenyl) methane.

The leuco dyes are described in British Pat. 1,047,796,

published Nov. 9, 1966; Italian Pat. 707,086, issued May 24, 1966 and in US. patent applications Ser. Nos. 363,638 and 363,639, both filed Apr. 29, 1964 and assigned to the assignee herein.

(D) The fixing component The fixing component is so named because when present it fixes the colored form of the leuco dye permanently. The fixing component can be any material which will maintain the permanent image. For example, a redox system such as described in British Pat. 1,057,785 is useful. The component described therein comprises an oxidant and a reductant which react with each other when irradiated With actinic light of a different wavelength than that used to activate the coumarin. The reaction between the oxidant and reductant forms a reducing agent which reacts with and deactivates the biimidazole. Thus leuco image will remain stable. Other qualifications of this system are that it is unreactive at the wavelengths used to activate the coumarin and that it is unreactive with the leuco dye at any wavelength. Examples of the oxidant include quinones, ketones, phenazines, acridines, phenoxazinones, quinolines, phenanthrolines, isoquinolines, and anils. Examples of the reductant include ethers, esters, alcohols, compounds containing allylic or benzylic hydrogen, i.e., containing a methylene group attached to a carbon that is itself attached to another carbon by a double bond, acetals, aldehydes and amides. Specific examples of such compounds are found in said British Pat. 1,057,785 and are incorporated herein.

Another type of fixing agent is an organic progenitor of a reducing agent which forms a reducing agent upon heat treatment, but is otherwise inert to the biimidazoleleuco dye imaging system. The reducing agent so formed then reacts with and deactivates the biimidazole. Generally, the heat necessary to transform the progenitor will be between 80 C. and 160 C. Examples of such progenitors include acetals, orthoesters, carbonates and orthocarbonates of hydroquinones and phenols such as hydroquinone, phenylhydroquinone, t-butylhydroquinone, durohydroquinone, p-benzylhydroquinone, naphthylene-lA-diol,

resorcinol, pyrogallol, 2,4,6-tri-tertbutylphenol, 2,6-ditert-butyl-p-cresol, and 2,4;6-trimethylphenol; semicarbazones of aldehydes and ketones; Schilfs bases of primary aromatic amines such as aniline and 1-naphthylamine; diketones which tautomerize to hydroquinones on heating such as 2,4-dihydro-1,4-naphthoquinone and 4a,5,8,8a-tetrahydro-l,4-naphthoquinone. These and other heat-sensitive progenitors are described more fully in Manos U.S. Ser. No. 363,625, filed Apr. 29, 1964, and assigned to the assignee herein.

Still another type of fixing agent are diazonium compounds which, upon exposure to radiation of a wavelength difierent than that which energizes the biimidazole, yield a reducing agent directly. The reducing agent then reacts with and deactivates the biimidazole. Examples of diazonium compounds include diazotized 4- (p-tolylthio o-anisidine 2,4,5 -trimethoxyaniline 5 -amino-2-diethylamino-p-anisic acid, methyl ester 4- p-tolyltihio) o-anisidine 4- 4-amino-3-butylphenyl morpholine 4- 4-amin0-2,5-diethoxyphenyl morpholine 4- 4-amino-2,5-dibut0xyphenyl) morpholine 4- p-aminophenyl) morpholine 4-amino-l-naphthol 4-amino-7-methoxy-3 -methyl-1naphthol 4-amino-3 -methyl-l-naphthol N ,N -dirnethyl-1,Z-naphthalenediamine N,N-diethyl-1,4-naphthalenediamine 2-methyl-N -phenyl-1,4-naphthalenediamine 4-amino-2,6-dimethoxyphenol N ,N -diethyl-4-methyl-m-phenylenediamine 4-methoxy-N ,N -dimethyl-m-phenylenediamine N,N-diethyl-o-phenylenediamine N ,N -diethyl-4-methyl-o-phenylenediamine N-methyl-N-phenyl-o-phenylenediamine p-phenylenediamine These fixing agents are described in Cescon US. patent application Ser No. 448,839, filed Apr. 16, 1965, and assigned to the assignee herein.

A preferred oxidant-reductant combination fixing agent comprises as oxidant pyrenequinone or phenanthrenequinone and as reductant a lower alkyl ester of nitrilotriacetic, nitrilo-tripropionic acid, dioxane, polyethylene gylcol, polypropylene glycol, polytetramethylene glycol, methoxyethyl terephthalate, cyclohexyl adipate, 1,3-cyclohexylene diacetate, or mixtures thereof. Preferably the reductant is a polyethylene glycol.

(E) Preferred composition ratios and other components As previously stated, the basic composition, for sunscreen shields, etc., is preferably composed of .1 to 2 moles of coumarin to 1 mole of the biimidazole, and most preferably .4 to .6 moles of coumarin per mole of biimidazo e.

For developing colored images through exposure to light, the biimidazole/near UV sensitizer/leuco dye combination will normally be employed in molar ratios 1/ .12/.110, preferably 1/.4-.6/.5-2.

Amounts of the oxidant-reductant fixing system will range from molar ratios of 0.01:1 to 2:1 of oxidant to biimidazole, with 0.2:1 to 0.5 :1 preferred. The reductant components can range from molar ratios of 11 to 40:1 of reductant to oxidant. Amounts of the organic progenitor fixing agent will range from molar ratios of 1:5 to 20:1 of progenitor to biimidazole. The diazonium fixing agent can range from ratios of 0.21 to 10:1 of agent to biimidazole.

Further, it will be normally advantageous to include other components in the imaging formulation, such as solvents, plasticizers and/or binders (0.5% by weight or more of each based on the total weight of imaging composition) to provide for intimate contact among the biimidazole, coumarin, leuco dye, and fixing system, and to facilitate their application to substrates in coating applications.

Suitable solvents are those inert to the other ingredients of the composition and include amide such as N,N-diiodide, 3,3'-diethyl-9-methyl oxacarbocyanine iodide, and 3,3',9-trimethyle thiacarbocyanine bromide; or cyanine dyes such as 1,1'-diethyl-2,2-dyanine iodide, 1,1'-diethyl 4,4'-cyanine iodide, and l,3',diethyl-4,2'-quinolyl thiacyanine iodide.

methylformamide, N,N-dimethylacetamide;alcohols such (F) Utility as methanol, ethanol, l-propanol, Z-propanol, butanol, ethylene gly c 01; ketones Such as acetone, methyl ethyl The compositions of this invention are useful tor lighttone, 3-pentanone; halocarbons such as methylene chloractuaied colored formatlon and are In y ide, chlorotorin, 1,1,2-trichloroethane, and 1,l,2,2-tetranolt'sflver photographlc process. capable of 1m.agmg.m chloroethane; polyethylene glycols; esters, e.g., ethyl acecolors and g on vanous Substrates .lcludmg tate and ethyl benzoate; aryls such as benzene, o-dichlorof Papers and slmflar fibrou? Sheet mammals and benzene and toluene; dimethylsulfoxide, pyridine, acem: APparatu? useful m conductmg photographic dyetonitrile, tetrahydrofuran, dioxane, 1,1,2-trichloroethylene, Punting descnbed Pats and 9 1-methyl-2-oxo-hexamethyleneirnine, and mixtures there- 5 Even Very Soft g as for exflinple i q Whlch of has been treated With a composition of this invention, can

Suitable inert plasticizers include the polyethyleneglybe readlly Pnnted by prolectmgflle i q graph: patcols, such as the commercially available Carbowaxes, and tern onto the treated paper and irradiating it to effect the related materials, such as substituted phenol-ethylene q t g oxide adducts for example the products obtained from p- T e llnagmg ormulatlons.are 9Onvem.enfly apphed to phenylphenol and 6 m 0168 ethylene oxides, and from the carrier substrates as solutions in volatile solvents such nonylphenol and 2 moles ethylene oxide, including comas those descnbed above They y. thus contliluously mercially available materials such as the Igepal alkyl CPated on roll.papers and.films utlhzmg Such typ 16.811 dephenoxy polyoxyethylene ethanols. vices for continuously laying down Wet films as nip fed Polymeric materials particularly light transparent and three roll reverse roll coating heads, gravure coaters, tra lfilm-forming polymers, are useful as inert binders, and mg coaiers Mayer bar coatlng heads carriers for the essential ingredients described above; thus, the g thlckness 1s i i i q threaded bi-imidazole, leuco dye, sensitizer and polymer, with or Woun The wet t w Hess lusted h t at t 6 without a mum a1 Solvent, may be mixed, then sprayed dry thickness after solvent removal is in the desired range extruded, cast, pressed or otherwise formed into supported g i i amimd a on paper or unsupported films or shaped articles. Representative on tert e 3 as 6.611 rergcved polymers are polyvinyl alcohol, ethyl cellulose, polyvinyl y g ail/[mg ordforce i g e mate chloride, polystyrene, polyvinyl acetate, poly(methyl il? or p up on m S e usua i methacrylate), cellulose acetate, cellulose butyrate, coy convemefnt 1g t.source provldmg Wave engths m polymers of vinyl monomers, gelatin, and polyethylene. the near ulpravlolet reiglon of the Spectrum that oviaflap Other suitable inert materials which may be used include the coumarilis absorptlqn bands m be usiid to actlvate glasses, resins and Waxes. the compositions for imidazolyl radical and mage forma- Typical inert substrates include materials commonly tion. The light may come from natural or art ficial sources, used in the graphic arts and in decorative applications, may be mPHOChrOmaUC or polychromatlc ntcoherent or such as paper ranging from tissue paper to heavy card 40 coherent (i.e. laser beams such as a pulsed nitrogen laser board; 'films of plastics and polymeric materials such as emlmng at 337 and for hlgh q p Should regenerated cellulose, cellulose acetate, cellulose nitrate, i g 5 E m Y h to the princlpal f g polyester of glycol and terephthalic acid, vinyl polymers an S t e cpumann sns.ltlzers emp oyefi and S 01.1] and copolymers, polyethylene, polyvinylacetate, Poly be sufliciently intense to activate a substantial proportion methyl methacrylate, polyvinylchloride; textile fabrics; of the Sensmzer molecules glass; Wood and metals. THE EXAMPLES In addition the Spectral Sensitivity of the compositions The following examples illustrate the com ositions of can be extended to the visible light range by incorporating this invention and their uses. p therein, either in conjunction With the coumarin or alone, visible light-absorbing energy transfer agents such as EXAMPLE 1 phthal in 1E -g-, f q i erythrosins, e0S il1S and Ultraviolet light sensitive biirnidazole compositions conha o aminvacrldine dy Such taining the following ingredients in parts by Weight were acridine hydrochloride, acriflavine and acridine orange; prepared as solutions in acetone, a convenient carrier carbocyanine dyes such as 3,3'-diethyl oxacarbocyanine solvent:

Composition Relative mttile Ingredient Control A G o-ClHAi I Acetone (solvent), grains. 46 46 46 Celluliost; acetate butyrate (a thermoplastic resin 6 6 11'] BI Polyethylene ether glycol, MW. 550 (a plasticizer 6 and the the reductant of the fixing system) 3 3 3 z-lrinettlgoayeftiig trlixhthaslageem) plasticizer and a re- 1 1 1 11 H 0 1H m a 2, 2'b is(och1orophen l)- 4, 4, 5-tetraphenyll, 2biigii igagljelgi-ClHABl) mnx.263m]l(h("/X31S,Ty1- 30 30 30 1 0 T mm ,Naiaiiiiiaiaasitayii5.13.1153;'iiaiei ye .53 p-Toluenesulfonic acid monohydrate (stabilizer for 67 the reduced leuco dye) .34 .34 .34 2.0 Pygezrkiliqgxirgiggigfig 1, 6 and 1, 8-isoiners (oxidant 04 O4 04 0 o 7-dimetz ylainiuo-4metliylcoumarin )nnx. 360 1 sensiizer 6 7-d iethylamino-4-metl1ylcoumarin max. l 0 tizer) A .19 1.0

1 5 The solutions were applied to bleached-sulfite roll stock paper and the acetone allowed to evaporate to give coatings about 0.5 mil thick. Each paper was then irradiated by contact flashing with one flash from a Xenon flash lamp (HiCo Lite, emitting ultraviolet light above 200 mu and 1 6 EXAMPLE 3 Imaging formulations were prepared as described in Example 1 except that (a) the quinone was omitted and (b) different coumarins, as identified below, were emapproximating ordinary unfiltered sunlight), directly and 5 ployed in amounts corresponding to 0.5 mole/mole 0- through a filter system transmitting from 340 to 420 mu C1HABI. Papers were coated with these formulations and with peak transmittance at 370 mu, obtained by overlayimaged as described in Example 2 through filter system C ing a Corning No. 754 filter (transmitting from 220 to except that a xenon arc lamp provided the radiation. The 420 mu) with a Corning No. 052 filter (transmitting results are tabulated below:

Imaging results Speed, O.D., 50 Coumarin sec sec Composition:

C 7-diethylami11o, 4-methyl 2. 2 1. 21 D 5,7-dimethoxy 3.8 1.09 E Tinopal PG- 2.9 0.99 Control 1 None 5.0 1.01 Control 2 7-diethylaminoA-rnethyl- No color formation coumarin but no o-C IHABI.

from 340 mu into the visible beyond 420 mu). The results were as follows:

Color formation Unfiltered UV Filtered UV Composition:

A Intense. Medium.

.do Medium-intense. Control o Faint green.

The less intense color formation obtained with the filtered (i.e. near UV) radiation is attributed to the fact that the particular filter system employed shows only 70% transmittance at the 370 m peak. The results show, however, that the coumarins enhance the sensitivity of the imaging formulation to near UV radiation.

This example also demonstrates the conversion of the biimidazole to the imidazolyl radical through action of the coumarin, as evidenced by the further reaction of the radical with the leuco dye.

EXAMPLE 2 Photosensitive papers prepared as described in Example 1 were exposed to ultraviolet radiation from a medium pressure mercury lamp, through filter systems A, B, C

described below:

The results show (1) the coumarins are highly effective sensitizers in the near UV; with 7-diethylamino-4-methylcoumarin more than doubling the speed and increasing the optical density 20%; (2) the coumarin alone, without the biimidazole is not a photooxidant for the leuco dye.

EXAMPLE 4 Imaging formulations were prepared as acetone solutions from the following ingredients, in parts by weight:

1 Produced from 1 mole of the phenol and 6 moles ethylene oxide; replacing this ingredient with the product obtained from pnonylphene1 and 2 moles ethylene oxide give substantially similar results.

3 2 9$7I116 uco dye, yielding a red oxoarylidene dye, as described in [7.8.

Appropriate controls were also prepared with no added coumarins. The solutions were applied to Mylar poly- Filter Components Remarks A Schott Filter UG-ll 'Iransmits from 230 mp. to 420 In with peak (90% transmission) at 320 my.

13 UG-ll over polyester film The polyester transmits from 315 m into the visible; the combination from 315 my. to 420 with peak (80% transmission) at 350 m C UG-11 over Corning Filter No. 0-52 0-52 Cuts oil light below 340 11111.; the combination transmits from 340 to 420 with peak transmission) at 370 m ester film and the acetone allowed to evaporate. The coated films were covered with a sharp cut off filter (Corning Filter No. 3-75), which transmits only 5% at 380 m 40% at 400 mo, and progressively more light at longer wavelengths, and irradiated by contact flashing as de scribed in Example 1. In each example, the coatings con- Filter A Filter B Filter C Coumarin Speed O.D. Speed O.D. Speed O.D.

Composition A 7'l\/IG2N, 4-Mo 3. 5 1. 03 6. 4 0. 89 11. 5 0. 58 'I-EtzN, 4-Me. 3, 0 1. l2 5. 7 0. 89 9. 5 0. 76 None 4. 0 l. 13 0. 8 0. 24. 3 0. 42

The results, particularly with filter systems B and C, show that the coumarins significantly enhance the spectral sensitivity of the biimidazole/leuco dye imaging system to near ultraviolet radiation.

taining the coumarin sensitizer produced strongly colored images, whereas the controls formed substantially no color.

1 7 EXAMPLE This example illustrates the use of cathode ray tubes as energy sources.

The formulation described in Example 4 as composition F (except that 36.8 instead of 46 parts acetone was employed) was coated on a bleached sulfite paper to a 0.5 mil thickness after acetone evaporation. A cathode ray tube with a P22B phosphor emitting from 390 to 550 m with peaking at 450 m and having a 1 x 2" standard television raster made up of a series of alphanumeric characters, was operated at a 20 kv. accelerating potential and an average raster current of 100 micoamperes. Under such conditions, contacting the photosensitive paper with the cathode ray tube face produced a colored image having an optical density of at least 0.3 in 0.5 second.

EXAMPLE OF A CATHODE RAY TUBE PRINTOUT SYSTEM Ultraviolet emitting cathode ray tubes for writing on photosensitive materials are particularly versatile light sources for use in imaging the subject compositions. These in general involve an ultraviolet emitting phosphor internal coating as the means for converting electrical energy to light energy and a fiber optic face plate as the means for directing the radiation to the photosensitive target. For purposes of this invention, the phosphors should emit strongly in the 320420 m range so as to substantially overlap the near UV-absorption characteristic of the coumarin-containing compositions. Representative phosphors include the P4B (emitting at 300-550 m peaking at 410 m P16 (330-460, peaking at 380 m and P22B (390- 510, peaking at 450 mn) types. (The Electronic Industries Association, New York, New York, assigns P-numbers and provides characterizing information on the phosphors; phosphors with the same P-number have substantially identical characteristics.)

In typical cathode ray tube printout systems, information to be recorded, which may originate from a computer, radar camera, infrared camera, TV camera or other central source, is fed to a command unit which in turn controls a function generator which transmits the information as signals (alpha-numerics, strokes, dots) that the cathodes ray tube can utilize and convert to a luminous pattern. For continuous imaging, a transport system conveys the photosensitive target (paper, cards or film) past the face of the tube and sends appropriate signals to the command unit to keep the imaging signals properly synchronized with the moving target. Such transport apparatus with auxiliary control and signal means is well known to the art and requires no further description. Related cathods ray tube printout systems are described in U.S. Pats. 3,289,196; 3,258,525; 3,235,658; 3,184,753; 3,041,947.

In such uses, the imaging compositions of this invention provide for high imaging speed, high resolution and good contrast in an essentially dry direct printout process. As the supports may vary widely, their use makes possible a multipurpose electronic information output system comprising a central electronic system feeding and operating a multiplicity of cathode ray tube printers, each capable of performing a separate function and of providing soft or hard copy.

The drawing schematically illustrates a digital computer output system, with a multiplicity of CRT image printers comprising; digital computer 1; device controller or command unit 2, to control the device from the computer and to inform the computer if the device needs servicing; buffer memory 3, to sequentially store binary information from 1 and subsequentially pass this information on to digital-to-analog (D to A) converters (described below); variable clock 8 and delay one shot 9, to provide a time base and a strobe signal for transferring information from 3 to the D to A converters; comparator 10 and AND gates 11, 12, 13 and 14, to choose the proper D to A converter to receive the information from 3; D to A converters 4, 5, 6 and 7, to convert the digital information from 3 to analog voltages and amplify the voltages to drive the horizontal and vertical deflection systems of ultraviolet fiber optic cathods ray tubes; cathode ray tubes 15 and 16 with UV-emitting phosphors and fiber optics; conveyors 17 and 18, to transport photosensitive paper and film (not shown), at the proper rates so that the resulting image is clear and distinct.

The digital output system operates in two major states; one, to read binary information with buffer memory 3; two, to write from 3 to cathods ray tubes 15 and 16. To read into 3, computer 1 commands controller 2; memory 3 signals the need for more data to controller 2, which signals computer 1 with a pulse. When going into this state, controller 2 sends signals to blank CRTs 15 and 16 and stop conveyors 17 and 18; it puts the memory 3 into the read state by signalling to reset the address register to zero, then disenables clock 8 with a pulse and sesets the counter in comparator 10 with a pulse. In the read state, controller 2 puts the data from 1 into proper sequence, so that the proper information gets to the D to A converters 4, 5, 6 and 7; it loads a flip-flop register in memory 3 with the data and reads the register in with a read pulse. When finished transferring the data, controller 2 unblanks CRTs 15 and 16 resets the address register in buffer 3 with a pulse, enables clock 8, starts conveyors 17 and 18 and controls their speed.

To write from buffer 3, controller 2 enables clock 8 with a second pulse, the clock being variable from 30 c.p.s. to 2 mo. and adjustable to the necessary flow of information to CRTs 15 and 16. Clock 8 relays the pulse to increment comparator 10, to cause a delayed-one-shot in 9, to read memory into buffer 3; such pulse (and each succeeding pulse) increments the memory address so that it can write sequentially one word into an output register. The

address register flip-flops of the memory 3 are directed through switches 20 in series into AND gate 21 that allows a pulse to go to controller 2 when the memory is empty. The delayed pulse from 9, which passes through AND gates 11, 12, 13 and 14, strobes the buffered word into digital-to-analog converters 4, 5, 6 and 7, with comparator 10 logically ANDing the strobe signal into the proper converter. Thus, memory 3 presents the binary information to D to As 4, 5, 6 and 7 which feed the signals to cathode ray tubes 15 and 16; which image the papers being conveyed past their faces by the conveyors 17 and 18.

The various components and associated electronics enumerated and referred to above, are known to those skilled in the art and available for use in digital computer/CRT printout systems, and need no further description.

If desired, additional CRTs can be added to the drawing system, each performing the same or different function. For example, a CRT with a 2" x 8" face plate images paper; while an identical CRT images cards; a third with a 1%" x 1% face plate images 16 mm. film, e.g., at 36 frames/ sec. for movies including alphanumerical and graphic movies, while a fourth with a 1%" x 1%" face plate images 35 mm. film for storage, blow back to large sizes, wall displays and read-only memories for the computer; all continuously generated by the computer. Thus the multiplicity of CRTs can replace a like multiplicity of the conventional peripheral readout equipments-Alternatively, ultraviolet lasers can be employed in place of the CRTs.

In other CRT'printouts embodiment, an ordinary TV receiver is modified to accommodate a second CRT, in parallel with the viewing picture tube, but as a printing head, along with a photosensitive paper supply and a transport means for moving the paper past the printing face on demand. In operation, a TV station generates two ditferent'video signals; one, standard programming is displayed on the picture tube, the otherwhich may be different from the other in both information and format, and

is generated by a TV camera or a computer character generator processing inputs from a wire service or other news sourceis separated from the first and routed to the printing tube which delivers the hard copy as continuous tone images. To obtain high print rates from a raster display format, a band scan method is employed. In this method a small analog computer generates a long period ramp (a linear current waveform applied to the deflection yoke to move the cathode ray beam linearly across the tube face.) The vertical 60 c.p.s. ramp taken from the TV camera is mixed with the computers ramp and a DC. bias level. With the composite vertical waveform, the camera slowly scans the object at a rate, r. On the printing tube, the object appears to move slowly across the screen. At the printing tube face, the paper to be imaged is driven at a constant rate, r, equal to the scan rate. Hence, the relative motion is zero during the contact printing stage. Band scanning is useful with any raster display and it is not limited to TV raster displays; it is useful in general for imaging continuously moving paper, permits the use of relatively small diameter or less) CRTs, and minimizes phosphor burning by minimizing the power density at the phosphor.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations are to be understood therefrom. The invention is not limited to the exact details shown and described, for obvious modifications will occur to those skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A photosensitive composition which comprises:

(A) a hexaarylbiimidazole that absorbs in the ultraviolet principally at wave lengths below 300 mu and is dissociable to triarylimidazolyl radicals by radiation of such wave lengths, and is represented by the structural formula NN N wherein X and Y are each hydrogen, lower alkyl or lower alkoxy; Z is hydrogen, lower alkyl, lower alkoxy or dilower alkylamino; W is hydrogen, lower alkyl, phenyl containing a lower alkoxy group in the 0 or p-position, or phenyl containing a substituted amino group in the 0 or p-position; and wherein at 29 least one of W and Z is other than hydrogen or lower alkyl.

2. The composition of claim 1 which contains additionally an oxidizable leuco dye selected from the group consisting of aminotriarylmethanes, aminoxanthenes, aminothioxanthenes, amino-9,IO-dihydroacridines, aminophenoxazines, aminophenothiazines, aminodihydrophenazines, aminodiphenylmethanes leuco indamines, aminohydrocinnamic acids, hydrazines, leuco indigoid dyes, amino-2,3-dihydroanthraquinones, tetrahalo p,p biphenols, 2(p-hydroxyphenyl)-4,5-diphenylimidazoles, phenethylanilines, l0-acyl-aminodihydrophenazines, lO-acylaminophenothiazines, 10 acyl aminophenoxazines, and aminotriarylmethanes wherein the methane hydrogen has been replaced by alkylthio, benzylthio, Z-phenylhydrazino or alkoxycarbonyl.

3. The composition of claim 2 which contains additionally an image fixing system comprising (A) a photooxidant which is activatable at wavelengths different from those required to activate the coumarin-biimidazole system, does not photooxidize leuco dye to dye, and is reducible in its photoactivated state to a second reductant, said photooxidant being selected from the class consisting of quinones, ketones, phenazines, acridines, phenoxazinones, quinolines, phenanthrolines, isoquinolines, and anils, and

(B) a first reductant which is a reductant for the photooxidant but not for the photoactivated biimidazole, said first reductant reducing the photoactivated photooxidant to the second reductant, said first reductant being selected from the class consisting of ethers, esters, alcohols, acetals, aldehydes, amides, and compounds containing allylic or benzylic hydrogen.

4. The composition of claim 2 wherein the leuco dye is a triarylmethane wherein at least two of the aryl groups are phenyl having a para-R R N substituent in which R and R are C C alkyl, 2-hydroxyethyl, Z-cyanoethyl, benzyl or phenyl, and having an ortho C C alkyl, C -C alkoxy, fluoro, chloro, or bromo substituent, and the third aryl group can be the same as the first two or can be thienyl, furyl, phenyl or substituted phenyl.

5. The composition of claim 1 wherein the coumarin is a 7diloweralkylamino-4-lower alkyl courmarin.

6. The composition of claim 1 wherein the coumarin is a 7-lower alkoxycournarin.

7. The composition of claim 1 wherein the coumarin is 7-diethylamino-4-methyl coumarin.

8. The composition of claim 1 wherein the A, B and D groups contain substituents having Hammett sigma values in the range .4 to +4.

9. The composition of claim 8 wherein each A is a phenyl ring bearing an ortho substituent selected from fluorine, chlorine, bromine, lower alkyl and lower alkoxy.

10. The composition of claim 9 wherein each B and D group is a phenyl ring.

11. The composition of claim 4 wherein the coumarin is 7-diethylamino-4-methyl coumarin; the biimidazole is 2-(o-chlorophenyl)-4,5-bis(m-methoxyphenyl) imidazolyl dimer and the leuco dye is an acid salt of trist(N,N-diethyl amino-o-tolyl methane.

12. A coating composition comprising the composition of claim 4 dissolved in an inert solvent.

13. A coating composition comprising the composition of claim 4 and an inert substrate.

14. The composition of claim 3 where the photooxidant is a quinone and the first reductant is an ether having abstractable hydrogen, an ester having abstractable hydrogen, a lower alkyl nitrilotriacetate or a lower alkyl nitrilotripropionate.

15. The composition of claim 14 wherein the photo oxidant is pyrenequinone or phenanthraquinone and the first reductant is a polyalkylene glycol or an aryl phenoxy polyoxyethylene ethanol.

(References 021 following page) 21 22 References Cited NORMAN G. TORCHIN, Primary Examiner UNITED STATES PATENTS R. E. FIGHTER, Assistant Examiner 3,39 ,994 7/1968 Cescon 96-90 X C1.

3,390,996 7/1968 MacLachlan 96-9OX 5 9683 

